Enhanced scattering in voltage sensitive encapsulated liquid crystal with spaced apart absorber

ABSTRACT

In the present invention encapsulated liquid crystal material in a support medium illuminated from the viewing side or direction will appear bright or white relative to background when in distorted alignment, e.g. in the absence of an electric field. Incident light impinging on the liquid crystal material is isotropically scattered thereby into the support medium, and using the principle of total internal reflection a relatively large part of the isotropically scattered light is reflected back to illuminate the distorted liquid crystal material tending to brighten the same so that light it scatters back to the viewing direction out of the support medium causes the liquid crystal material to appear relatively light or bright as compared to the background where there is no liquid crystal material or where the liquid crystal material is in parallel alignment in field-on condition, i.e. aligned with respect to an electric field, and, thus, substantially transmissive. Original incident light where there is no liquid crystal material, that light which is isotropically scattered toward the back or non-viewing side of the display and within a certain cone or solid angle, and that light passing through aligned (field-on) liquid crystal material will tend not to be totally internally reflected; such light will pass through the support medium and may be absorbed by a remote black or colored material. Moreover, principles of optical interference may be employed further to enhance the apparent brightness of the liquid crystal material.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of copending U.S. patent application Ser.No. 477,138, filed Mar. 21, 1983, which is a continuation-in-part ofU.S. patent application Ser. No. 302,780, filed Sept. 16, 1981, now U.S.Pat. No. 4,435,047.

Reference additionally is made to U.S. patent application Ser. No.477,242, filed Mar. 21, 1983. Such additional application also is acontinuation-in-part of Ser. No. 302,780. The entire disclosures of suchapplications and patent, which are commonly assigned with thisapplication, are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates generally to the art of liquid crystalsand more particularly to the scattering of light by liquid crystalmaterial. Moreover, the invention relates to use of such scattering in aliquid crystal display apparatus to form a white or bright character andin optical shutter devices, e.g. to control brightness. The inventionalso relates to enhancing of the light output/contrast of a liquidcrystal apparatus, especially of the type using encapsulated liquidcrystal or liquid crystal material held in a containment medium, such asan emulsion. The invention further relates to methods of making andusing such liquid crystal apparatus.

BACKGROUND

Liquid crystal material currently is used in a wide variety of devices,including, for example, optical devices such as visual displays. Aproperty of liquid crystals enabling use in visual displays is theability to scatter and/or to absorb light when the liquid crystals arein a random alignment and the ability to transmit light when the liquidcrystals are in an ordered alignment.

Frequently a visual display using liquid crystals displays darkcharacters on a gray or relatively light background. In variouscircumstances it would be desirable, though, using liquid crystalmaterial to be able to display with facility relatively brightcharacters or other information, etc. on a relatively dark background.It would be desirable as well to improve the effective contrast betweenthe character displayed and the background of the display itself.

An example of electrically responsive liquid crystal material and usethereof is found in U.S. Pat. No. 3,322,485. Certain types of liquidcrystal material are responsive to temperature, changing the opticalcharacteristics, such as the random or ordered alignment of the liquidcrystal material, in response to temperature of the liquid crystalmaterial.

Currently there are three categories of liquid crystal materials, namelycholesteric, nematic and smectic. The present invention preferably usesnematic liquid crystal material or a combination of nematic and somecholesteric type. More specifically, the liquid crystal materialpreferably is operationally nematic, i.e. it acts as nematic materialand not as the other types. Operationally nematic means that in theabsence of external fields structural distortion of the liquid crystalis dominated by the orientation of the liquid crystal at its boundariesrather than bulk effects, such as very strong twists as in cholestericmaterial, or layering as in smectic material. Thus, for example, chiralingredients which induce a tendency to twist but cannot overcome theeffects of boundary alignment still would be operationally nematic. Suchmaterial should have a positive dielectric anisotropy. Although variouscharacteristics of the various liquid crystal materials are described inthe prior art, one known characteristic is that of reversibility.Particularly, nematic liquid crystal material is known to be reversible,but cholesteric material ordinarily is not reversible.

It is also known to add pleochroic dyes to the liquid crystal material.One advantage to using pleochroic dye with the liquid crystal materialis the eliminating of a need for a polarizer. However, in the nematicform a pleochroic device has relatively low contrast. In the pastcholesteric material could be added to the nematic material togetherwith the dye to improve contrast ratio. See for example the White et alarticle in Journal of Applied Physics, Vol. 45, No. 11, November 1974,at pages 4718-4723. However, although nematic material is reversible,depending on whether or not an electric field is applied across thesame, cholesteric material ordinarily would not tend to its originalzero field form when the electric field would be removed. Anotherdisadvantage to use of pleochroic dye in solution with liquid crystalmaterial is that the absorption of the dye is not zero in the field-oncondition; rather, absorption in the field-on condition follows anordering parameter, which relates to or is a function of the relativealignment of the dyes.

Usually liquid crystal material is anisotropic both optically(birefringence) and, for example in the case of nematic material,electrically. The optical anisotropy is manifest by the scattering oflight when the liquid crystal material is in random alignment, and thetransmission of light through the liquid crystal material when it is inordered alignment. The electrical anisotropy may be a relationshipbetween the dielectric constant or dielectric coefficient with respectto the alignment of the liquid crystal material.

In the past, devices using liquid crystals, such as visual displaydevices, have been relatively small. Use of encapsulated liquid crystalsdisclosed in applicant's above mentioned co-pending application hasenabled the satisfactory use of liquid crystals in relatively large sizedisplays, such as billboards, etc., as is disclosed in such application;and another large (or small) scale use may be as an optical shutter tocontrol passage of light from one area into another, say at a window orwindow-like area of a building. The present invention relates toimprovements in such encapsulated liquid crystals and to the utilizationof the light scattering characteristic of the liquid crystal material asopposed, for example, to the light absorption (usually with pleochroicdye) characteristic thereof. The invention also relates to the use ofsuch material and characteristics, for example, to obtain a relativelybright character or information displayed on a relatively dark orcolored background in both small and large displays as an opticalshutter, and so on. Such large displays and shutters may be about onesquare foot surface area or even larger. In accordance with the presentinvention the liquid crystal material most preferably is of theencapsulated type.

As used herein with respect to the present invention, encapsulatedliquid crystal material means liquid crystal material in a substantiallyclosed containment medium, such as discrete capsules or cells, andpreferably may be in the form of an emulsion of the liquid crystalmaterial and the containment medium. Such emulsion should be a stableone. Various methods for making and using encapsulated liquid crystalmaterial and apparatus associated therewith are disclosed below and inapplicant's copending application, which is incorporated by reference.

To facilitate comprehension of the invention relative to conventionalprior art liquid crystal displays, one typical prior art display isdescribed here. Such a prior display may include a support medium andliquid crystal material supported thereby. The display is relativelyflat and is viewed from a viewing side or direction from which aso-called front or top surface of the display is viewed. The back orbottom surface of the support medium may have a light reflective coatingtending to make the same appear relatively bright in comparison torelatively dark characters formed at areas where there is liquid crystalmaterial. (Back, front, top, bottom, etc. are used herein in general andwith reference to the drawings only for convenience; there is noconstraint that in operation the viewing direction must be, for example,from only the top, etc.). When the liquid crystal material is in orderedalignment, for example in response to application of an electric fieldthereto, incident light from the viewing direction passes through theliquid crystal material to the light reflective coating and also wherethere is no liquid crystal material passes directly to the lightreflective coating; and no character is observed from the viewingdirection. However, when the liquid crystal material is in randomalignment, it will absorb some and scatter some incident light therebyto form a relatively dark character on a relatively light colorbackground, for example of gray or other color depending on the type oflight reflective coating mentioned above, which still continues toreflect incident light where there is no liquid crystal material orwhere some liquid crystal material is in ordered alignment. In this typeof display it is undesirable for the liquid crystal material to scatterlight because some of that scattered light will be directed back in theviewing direction thereby reducing the darkness or contrast of thecharacter relative to the background of the display. Pleochroic dyeoften is added to the liquid crystal material to increase absorbenceand, thus, contrast when the liquid crystal material is in randomalignment.

BRIEF SUMMARY OF INVENTION

Succinctly stated, the disclosure relates to the isotropic scattering oflight by liquid crystal material and to the use of such isotropicallyscattered light to yield a white or bright appearance, character,information, etc., especially relative to background, when a liquidcrystal material is in a field-off or distorted alignment condition anda colored or dark appearance, e.g. the same as background, when a liquidcrystal material is in field-on parallel or ordered alignment condition.Preferably the liquid crystal material is nearly completelyisotropically scattering when in distorted alignment. Isotropicscattering means that when a beam of light enters the liquid crystalmaterial there is virtually no way to predict the exit angle ofscattered light.

As it is used herein with respect to the invention, the terms distortedalignment, random alignment and field-off condition mean essentially thesame thing; namely, that the directional orientation of the liquidcrystal molecules is distorted to an effectively curved configuration.Such distortion is effected, for example, by the wall of respectivecapsules. The particular distorted alignment of liquid crystal materialin a given capsule usually always will be substantially the same in theabsence of an electric field.

On the other hand, as it is used herein with respect to the invention,parallel aligned, ordered alignment, and field-on condition means thatthe liquid crystal material in a capsule is generally aligned withrespect to an externally applied electric field.

In accordance with one aspect of the present invention, a liquid crystaldisplay can produce relatively bright or white characters, information,etc., on a relatively dark background; the bright character is producedby liquid crystal material that is randomly aligned; the background iscaused, for example, by liquid crystal material that is in orderedalignment and, thus, substantially optically transparent and/or by areasof the display where there is no liquid crystal material. When theliquid crystal material is in parallel or ordered alignment, only therelatively dark background, e.g., formed by an absorber, would appear.The foregoing is accomplished using relatively low power requirements,minimum liquid crystal material, and illumination either from theviewing side or direction or from the back or non-viewing side of thedisplay. The principles of the invention also may be used in an opticalshutter or light control device to control brightness, for example.

Briefly, the liquid crystal apparatus includes liquid crystal materialfor selectively primarily scattering or transmitting light in responseto a prescribed input and a support medium for holding therein theliquid crystal material. In accordance with a preferred embodiment andbest mode of the invention, the liquid crystal material is of theencapsulated type that will cause substantially isotropic scattering oflight incident thereon, including the scattering of some of such lightback in the viewing direction toward, for example, the eye of anobserver. More preferably, such liquid crystal is operationally nematic,has a positive dielectric anisotropy, and has an ordinary index ofrefraction that substantially matches that of the containment orencapsulating medium therefor.

In one embodiment, a large quantity of light that is isotropicallyscattered by the liquid crystal material is totally internally reflectedby the support medium back to the liquid crystal material therebyilluminating the same and causing further isotropic scattering andbrightening of the appearance of the liquid crystal material, forexample to the eye of an observer. The internal reflectancecharacteristic of the support medium may be effected by the interface ofsuch back surface with another medium, such as a solid, liquid, or gas,even including air, with the constraint that the index of refraction ofthe support medium is greater than the index of refraction of such othermedium. The support medium may be comprised of several components,including, for example, the containment/encapsulating material (or thatwith which the liquid crystal material is in emulsion), additionalquantities of such encapsulating or other material, a mounting medium,such as a plastic-like film or glass, etc., all of which will bedescribed in further detail below.

The back surface of the support medium may be optically transmissive sothat light that reaches such surface in a direction substantially normalthereto will be transmitted. A light absorbing black or colored materialbeyond such back surface can help darken or color the apparentbackground on which the characters formed by liquid crystal materialappear. Ordered alignment of the liquid crystal material will at leastsubstantially eliminate the isotropic scattering so that substantiallyall the light passing through the liquid crystal material will also passthrough the back surface of the support medium.

In an alternate embodiment, a tuned dielectric coating may be applied,e.g. by evaporation techniques, to the back surface of the supportmedium to effect selective constructive and destructive opticalinterference. The thickness of such tuned dielectric coating will be afunction of lambda (α) divided by 2, lambda being the wavelength oflight employed with the apparatus. Constructive interference willenhance the internal reflection, especially by reducing the solid anglewithin which light would not be totally internally reflected in thesupport medium; and, therefore, such interference will further brightenthe appearance of the liquid crystal material characters.

Incident illumination for a liquid crystal display embodying theinvention may be from the front or viewing side. Alternatively, incidentillumination may be from the back side, preferably through a mask ordirector to direct light fully transmitted by the liquid crystalmaterial out of the field or angle of view at the viewing side. However,light scattered by the liquid crystal material within the viewing anglewould be seen.

Moreover, a cholosteric material may be added to the nematic liquidcrystal material to expedite return of the latter to distorted alignmentpattern following in general the configuration of the capsule or cellwall when the electric field is turned off, especially when the capsulesare relatively large. Also, if desired, a viscosity controlling additivemay be mixed with the liquid crystal. Further, an additive to the liquidcrystal may be used to help force a preferred alignment of the liquidcrystal structure in a capsule.

These and other embodiments of the invention will become apparent as thefollowing description proceeds.

A primary object of the present invention is to provide improvements inliquid crystal apparatus.

Another primary object is to effect selective substantially isotropicscattering of light using liquid crystal material, especially of theoperationally nematic type.

Still another primary object is to provide the various features andobjects of the invention in large size displays, in relatively smallsize displays and in optical shutters or other light control devices.

Another object is to enhance the optical output and contrast of liquidcrystal apparatus.

An additional object is to display white or bright characters,information or the like on a relatively dark background using liquidcrystal apparatus.

A further object is to use the principle of total internal reflection toenhance operation of liquid crystal apparatus, particularly a liquidcrystal display, and especially to enhance the use of isotropicallyscattered light to provide the desired output.

Even another object is to use the principles of optical interference toenhance the optical output of a liquid crystal apparatus, particularly aliquid crystal display.

Even an additional object is to scatter light isotropically in a liquidcrystal apparatus and to use such isotropically scattered light tocreate a bright character on a relatively dark background.

Even a further object is to improve the contrast of a liquid crystalapparatus.

Still another object is to improve the versatility of liquid crystaloptical devices.

Still an additional object is to provide a method for making a liquidcrystal apparatus.

Still a further object is to use liquid crystal apparatus in small andlarge scale devices, especially employing encapsulated liquid crystalmaterial.

Yet another object is to provide incident illumination for a liquidcrystal device from the non-viewing side thereof, and especially toprovide bright characters on a relatively dark background when usingsuch illumination.

Yet an additional object is to facilitate and/or to expedite the returnof encapsulated operationally nematical liquid crystal material to afield-off random or distorted alignment.

Yet a further object is to minimize the amount of liquid crystalmaterial required for a particular function, optical device, etc.

Even another object is to help force the liquid crystal structure in acapsule to a preferred orientation therein when in a field-offcondition.

These and other objects and advantages of the present invention willbecome more apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawings setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of but afew of the various ways in which the principles of the invention may beemployed.

BRIEF DESCRIPTION OF DRAWINGS

In the annexed drawings:

FIG. 1 is a schematic representation of a liquid crystal device inaccordance with the present invention;

FIGS. 2 and 3 are enlarged schematic illustrations of a liquid crystalcapsule in accordance with the present invention respectively under ano-field or field-off condition and under an applied electric field orfield-on condition;

FIGS. 4 and 5 are schematic representations of a liquid crystalapparatus according to one embodiment of the invention, respectively ina no-field condition and in an applied electric field condition;

FIG. 6 is a schematic representation of another embodiment of a liquidcrystal apparatus in accordance with the present invention using an airgap to cause total internal reflection;

FIGS. 7 and 8 are schematic representations of another embodiment ofliquid crystal apparatus in accordance with the present inventionemploying optical interference principles respectively under a no-fieldcondition and under an applied electric field condition;

FIG. 9 is an isometric view of a liquid crystal display apparatus inaccordance with the present invention and which may be formed of any ofthe embodiments disclosed herein;

FIG. 10 is a fragmentary schematic elevation view of another embodimentof liquid crystal apparatus using continuous layers of liquid crystalmaterial and interrupted electrodes;

FIG. 11 is a schematic isometric view, partly broken away, of theembodiment of FIG. 10;

FIG. 12 is a schematic view of an approximately proportioned liquidcrystal display according to the invention showing a more accuratelyrepresentative size relationship of the support medium layers andencapsulated liquid crystal layer for the several embodiments herein;

FIG. 13 is a schematic illustration of a nematic liquid crystal capsulewith cholosteric material additive, which may be used with the severalembodiments herein;

FIGS. 14 and 15 are schematic illustrations of still another embodimentof liquid crystal apparatus with a light control film director providedwith incident illumination from the non-viewing side, respectively, inthe field on and field off conditions;

FIG. 16 is a schematic illustration similar to FIGS. 14 and 15 but withthe light control film director cemented to the support medium; and

FIG. 17 is a schematic illustration like FIGS. 2 and 3 showing analternate embodiment of encapsulated liquid crystal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring in detail to the drawings, wherein like reference numeralsdesignate like parts in the several figures, and initially to FIGS. 1, 2and 3, encapsulated liquid crystal material used in accordance with thepresent invention is illustrated. In FIG. 1 is a schematicrepresentation of a liquid crystal apparatus 10 in accordance with thepresent invention. The apparatus 10 includes encapsulated liquid crystalmaterial 11 represented by a single capsule in FIGS. 1-3. Although thecapsules illustrated in the drawings are shown in two dimensions and,therefore, planar form, it will be appreciatd that the capsules arethree dimensionally, most preferably spherical. The capsule 11 is shownmounted in a preferably transparent support medium 12 having upper andlower portions 12a, 12b which may be integral with each other. Theapparatus 10 also includes a pair of electrodes 13, 14 for applying anelectric field across the liquid crystal material when a switch 15 isclosed to energize the electrodes from a conventional voltage source 16.

A primary feature of the present invention is that such encapsulatedliquid crystal material will isotropically scatter light impingingthereon when in a field-off random alignment condition; and in thefield-on orderly aligned condition, such material will be substantiallyoptically transparent.

It is to be understood that the capsule 11 may be one of many capsulesthat are discretely formed or, more preferably, that are formed bymixing the liquid crystal material with a so-called encapsulatingmaterial or containment medium to form an emulsion, preferably a stableone. The emulsion may be applied to or sandwiched between the supportmedia portions 12a, 12b, and electrodes 13, 14, as is illustrated. Ifdesired, the support medium 12 and the so-called encapsulating materialor containment medium may be the same material. As a furtheralternative, the upper and lower support medium portions 12a, 12b, orone of them, may be a plastic-like, glass, or like, preferablytransparent, mounting material. In this latter case the electrodes 13,14 may be applied to such mounting material and the encapsulated liquidcrystal material/emulsion, including many capsules 11, for example, maybe sandwiched between such mounting material 12a, 12b to form theapparatus 10, as will be described in further detail below.

A reflectance medium 18 forms an interface 19 with the lower supportmedium portion 12b to obtain the desired total internal reflectionfunction, which will be described in greater detail below. Suffice it tosay here, though, that due to the total internal reflection principle ofoperation, the liquid crystal material in the capsule 11 will beilluminated by incident light, for example represented by a light beam17, and with light that it isotropically scatters in the apparatus 10 sothat from the viewing area 20 beyond the upper support medium portion12a, the liquid crystal material 11 will appear white or relativelybright when under a no-field condition, e.g. the switch 15 is open.Although such isotropic scattering (and some absorption, especially witha pleochroic dye present in the encapsulated liquid crystal material)occurs in applicant's invention disclosed in the above co-pendingapplication Ser. No. 302,790, the total internal reflection principle ofthe present invention enhances scattering and, thus, brightens thevisual/optical appearance of characters formed by the encapsulatedliquid crystal material. A light absorbing layer 21 of black or coloredmaterial may be applied to the bottom or back surface of the reflectancemedium 18 remote from the interface 19 to absorb light incident on thelayer 21.

The electrode 13 may be, for example, a quantity of vacuum depositedindium tin oxide applied to the lower support medium portion 12b, andthe electrode 14 may be, for example, electrically conductive inkapplied directly to the liquid crystal material or could be like theelectrode 13. Other electrode material and mounting means therefor alsomay be used for either electrode. Examples include tin oxide andantimony doped tin oxide. Preferably the electrodes are relatively thin,for example, about 200 angstroms thick, and transparent so that they donot significantly affect the optics of the liquid crystal apparatus 10.

The encapsulated liquid crystal material 11 includes liquid crystal 30contained within the confines or interior volume 31 of a capsule 32.Each capsule 32 may be a discrete one or alternatively the liquidcrystal 30 may be contained in a stable emulsion of a containment mediumor so-called encapsulating material 33 that tends to form a multitude ofcapsule-like environments for containing the liquid crystal material.For convenience of illustration, the capsules 32 are shown as discretecapsules in and preferably formed of the overall quantity of containmentmedium or encapsulating material 33. According to the preferredembodiment and best mode of the present invention, the capsule 32 isgenerally spherical, and the liquid crystal 30 is nematic oroperationally nematic liquid crystal material having positive dielectricanisotropy. However, the principles of the invention would apply whenthe capsule 32 is of a shape other than spherical; such shape shouldprovide the desired optical and electrical characteristics that willsatisfactorily coact with the optical characteristics of the liquidcrystal material 30, e.g. index of refraction, and will permit anadequate portion of the electric field to occur across the liquidcrystal 30 itself for effecting desired ordered or parallel alignment ofthe liquid crystal when it is desired to have a field-on condition. Theshape also should tend to distort the liquid crystal material when in afield-off or random alignment condition. A particular advantage to thepreferred spherical configuration of the capsule 32 is the distortion iteffects on the liquid crystal 30 therein when in a field-off condition.This distortion is due, at least in part, to the relative sizes of thecapsules and the pitch of the liquid crystal; they preferably are aboutthe same or at least about the same order of magnitude. Moreover,nematic liquid crystal material has fluid-like properties thatfacilitate the conformance or the distortion thereof to the shape of thecapsule wall in the absence of an electric field. On the other hand, inthe presence of an electric field such nematic material will relativelyeasily change to ordered alignment with respect to such field.

Liquid crystal material of a type other than nematic or combinations ofvarious types of liquid crystal material and/or other additives may beused with or substituted for the preferred nematic liquid crystalmaterial as long as the encapsulated liquid crystal is operationallynematic. However, cholesteric and smectic liquid crystal materialgenerally are bulk driven. It is more difficult to break up the bulkstructure thereof for conformance to capsule wall shape and energyconsiderations in the capsule.

Turning to FIGS. 2 and 3, a schematic representation of the singlecapsule 32 containing liquid crystal 30 is shown, respectively, in thefield-off and field-on conditions. The capsules 32 are spherical andhave a generally smooth curved interior wall surface 50 defining theboundary for the volume 31. The actual dimensional parameters of thewall surface 50 and of the overall capsule 32 are related to thequantity of liquid crystal 30 contained therein and possibly to othercharacteristics of the individual liquid crystal material therein.Additionally, the capsule 32 applies a force to the liquid crystals 30tending to pressurize or at least to maintain substantially constant thepressure within the volume 31. As a result of the foregoing, and due tothe surface wetting nature of the liquid crystal, the liquid crystalswhich ordinarily in free form would tend to be parallel, althoughperhaps randomly distributed, are distorted to curve in a direction thatgenerally is parallel to a relatively proximate portion of the interiorwall surface 50. Due to such distortion the liquid crystals storeelastic energy. For simplicity of illustration, a layer 51 of liquidcrystal molecules whose directional orientation is represented byrespective dashed lines 52 is shown in closest proximity to the interiorwall surface 50. The directional orientation of the liquid crystalmolecules 52 is distorted to curve in the direction that is parallel toa proximate area of the wall surface 50. The directional pattern of theliquid crystal molecules away from the boundary layer 52 within thecapsule is represented by 53. The liquid crystal molecules aredirectionally represented in layers, but it will be appreciated that themolecules themselves are not confined to such layers. Thus, theorganization in an individual capsule is predetermined by theorganization of the structure 52 at the wall and is fixed unless actedon by outside forces, e.g. an electric field. On removal of the electricfield the directional orientation would revert back to the original one,such as that shown in FIG. 2.

Nematic type material usually assumes a parallel configuration andusually is optical polarization direction sensitive. However, since thematerial 52 in the encapsulated liquid crystal 11 is distorted or forcedto curved form in the full three dimensions of the capsule 32, suchnematic liquid crystal material in such capsule takes on an improvedcharacteristic of being insensitive to the direction of opticalpolarization of incident light. The inventor has discovered, moreover,that when the liquid crystal material 30 in the capsule 32 haspleochroic dye dissolved therein, such dye, which ordinarily also wouldbe expected to have optical polarization sensitivity, no longer ispolarization sensitive because the dye tends to follow the same kind ofcurvature orientation or distortion as that of the individual liquidcrystal molecules 52.

The liquid crystal 30 in the capsule 32 has a discontinuity 55 in thegenerally spherical orientation thereof due to the inability of theliquid crystal to align uniformly in a manner compatible with parallelalignment with the wall 50 and a requirement for minimum elastic energy.Such discontinuity is in three dimensions and is useful to effect adistorting of the liquid crystal 30 further to decrease the possibilitythat the liquid crystal 30 would be sensitive to optical polarizationdirection of incident light. The discontinuity protrusion 55 would tendto cause scattering and absorption within the capsule, and thetangential or parallel alignment of the liquid crystal molecules withrespect to portions of the interior wall surfaces 50 of the capsulesboth cause scattering and absorption within the capsule 32. When theelectric field is applied, for example, as is shown in FIG. 3, thediscontinuity will no longer exist so that such discontinuity will havea minimum effect on optical transmission when the encapsulated liquidcrystal 11 is in a field-on or aligned condition.

Although the foregoing discussion has been in terms of a homogeneousorientation of the liquid crystal material (parallel to the capsulewall), such is not a requisite of the invention. All that is required isthat the interaction between the wall and the liquid crystal produce anorientation in the liquid crystal near that wall that is generallyuniform and piecewise continuous, so that the spatial averageorientation of the liquid crystal material over the capsule volume isstrongly curved and there is no substantial parallel direction oforientation of the liquid crystal structure in the absence of anelectric field. It is this strongly curved orientation that results inthe scattering and polarization insensitivity in the field-offcondition, which is a feature of this invention.

In the field-on condition, or any other condition which results in theliquid crystal being in ordered or parallel alignment, as is shown inFIG. 3, the encapsulated liquid crystal 11 will transmit substantiallyall the light incident thereon and will tend not to be visible in thesupport medium 12. On the other hand, in the field-off condition whenthe liquid crystal is in distorted alignment, sometimes referred toherein as random alignment, for example as is shown in FIG. 2, some ofthe incident light will be absorbed, but also some of the incident lightwill tend to be scattered isotropically in the support medium 12. Usingtotal internal reflection such isotropically scattered light can beredirected to the encapsulated liquid crystal 11 thus brightening thesame tending to cause it to appear white to a viewer or viewinginstrument.

The index of refraction of the encapsulating medium 32 and the ordinaryindex of refraction of the liquid crystal 30 should be matched as muchas possible when in the field-on or liquid crystal orderly alignedcondition to avoid optical distortion due to refraction of incidentlight passing therethrough. However, when the liquid crystal material isin distorted or random alignment, i.e. there is no field applied, therewill be a difference in the indices of refraction at the boundary of theliquid crystal 30 and wall of capsule 32; the extraordinary index ofrefraction of the liquid crystal is greater than the index of refractionof the encapsulating medium. This causes refraction at that interface orboundary of the liquid crystal material and of the containment orencapsulating medium and, thus, further scattering. Light that is sofurther scattered will be internally reflected for further brighteningin the liquid crystal appearance. Such occurrence of different indicesof refraction is known or birefringence. Principles of birefringence aredescribed in Optics by Sears and in Crystals And The PolarizingMicroscope by Hartshorne and Stewart, the relevant disclosures of whichare hereby incorporated by reference. Preferably the encapsulating orcontainment medium 32 and the support medium 12 have the same index ofrefraction to appear optically substantially as the same material, thusavoiding a further optical interface.

As long as the ordinary index of refraction of the liquid crystalmaterial is closer to the index of refraction of the so-calledencapsulating PG,18 medium, than is the extraordinary index ofrefraction, a change in scattering will result when going from field-onto field-off conditions, and vice-versa. Maximum contrast results whenthe ordinary index of refraction matches the index of refraction of themedium. The closeness of the index matching will be dependent on thedesired degree of contrast and transparency in the device, but theordinary index of refraction of the crystal and the index of the mediumwill preferably differ by no more than 0.03, more preferably 0.01,especially 0.001. The tolerated difference will depend upon capsulesize.

According to the preferred embodiment and best mode, desirably theelectric field E shown on FIG. 3 is applied to the liquid crystal 30 inthe capsule 32 for the most part rather than being dissipated or droppedsubstantially in the encapsulating material. There should not be asubstantial voltage drop across or through the material of which thewall 54 of the capsule 32 is formed; rather, the voltage drop shouldoccur across the liquid crystal 30 within the volume 31 of the capsule32.

The electrical impedance of the encapsulating medium preferably shouldin effect be large enough relative to that of the liquid crystal in theencapsulated liquid crystal 11 that a short circuit will not occurexclusively through the wall 54, say from point A via only the wall topoint B, bypassing the liquid crystal. Therefore, for example, theeffective impedance to induced or displacement current flow through orvia only the wall 54 from point A to point B should be greater than theimpedance that would be encountered in a path from point A to point A'inside the interior wall surface 50, through the liquid crystal material30 to point B' still within the volume 31, ultimately to point B again.This condition will assure that there will be a potential differencebetween point A and point B. Such potential difference should be largeenough to produce an electric field across the liquid crystal materialthat will tend to align the same. It will be appreciated that due togeometrical considerations, namely the length through only the wall frompoint A to point B, for example, such condition still can be met eventhough the actual impedance of the wall material is lower than that ofthe liquid crystal material therein.

The dielectric constants (coefficients) of the material of which theencapsulating medium is formed and of which the liquid crystal iscomprised, and the effective capacitance values of the capsule wall 54,particularly in a radial direction and of the liquid crystal acrosswhich the electric field E is imposed, all should be so related that thewall 54 of the capsule 32 does not substantially drop the magnitude ofthe applied electric field E. Ideally the capacitance dielectricconstants (coefficients) of the entire layer 34 (FIG. 4) of encapsulatedliquid crystal material should be substantially the same for thefield-on condition.

The liquid crystal 30 will have a dielectric constant value that isanisotropic. It is preferable that the dielectric constant (coefficient)of the wall 54 be no lower than the dielectric constant (coefficient) ofthe anisotropic liquid crystal material 30 to help meet the aboveconditions for optimum operation. It is desirable to have a relativelyhigh positive dielectric anisotropy in order to reduce the voltagerequirements for the electric field E. The differential between thedielectric constant (coefficient) for the liquid crystal 30 when noelectric field is applied, which should be rather small, and thedielectric constant (coefficient) for the liquid crystal when it isaligned upon application of an electric field, which should berelatively large, should be as large as possible. The dielectricconstants (coefficients) relationships are discussed in the concurrentlyfiled application, the entire disclosure of which is specificallyincorporated by reference here. It should be noted, in particular,though, that the critical relationship of dielectric values and appliedelectric field should be such that the field applied across the liquidcrystal material in the capsule(s) is adequate to cause alignment of theliquid crystal structure with respect to the field. The lower dielectricvalues of commonly used liquid crystals are, for example, from as low asabout 3.5 to as high as about 8.

The capsules 32 may be of various sizes. The smaller the size, though,the higher the requirements will be for the electric field to effectalignment of the liquid crystal in the capsule. Preferably, though, thecapsules should be of uniform size parameters so that the variouscharacteristics, such as the optical and electrical characteristics, ofan apparatus, such as a display, using the encapsulated liquid crystalwill be substantially uniform. Moreover, the capsules 32 should be atleast 1 micron in diameter so they appear as discrete capsules relativeto an incident light beam; a smaller diameter would result in the lightbeam "seeing" the capsules as a continuous homogeneous layer and wouldnot undergo the required isotropic scattering. Examples of capsulesizes, say from 1-30 microns diameter, and of liquid crystal materialare in the above concurrently filed application and are herebyspecifically incorporated by reference.

A preferred liquid crystal material in accordance with the best mode ofthe invention is that nematic material NM-8250, an ester sold byAmerican Liquid Xtal Chemical Corp., Kent, Ohio, U.S.A. Other examplesmay be ester combinations, biphenyl and/or biphenyl combinations, andthe like.

Several other types of liquid crystal material useful according to theinvention include the following four examples, each being a recipe forthe respective liquid crystal materials. The so-called 10% material hasabout 10% 4-cyano substituted materials; the 20% material has about 20%4-cyano substituted materials, and so on.

    ______________________________________                                        10% Material                                                                  Pentylphenylmethoxy Benzoate                                                                          54     grams                                          Pentylphenylpetnyloxy Benzoate                                                                        36     grams                                          Cyanophenylpentyl Benzoate                                                                            2.6    grams                                          Cyanophenylheptyl Benzoate                                                                            3.9    grams                                          Cyanophenylpentyloxy Benzoate                                                                         1.2    grams                                          Cyanophenylheptyloxy Benzoate                                                                         1.1    grams                                          Cyanophenyloctyloxy Benzoate                                                                          9.94   grams                                          Cyanophenylmethoxy Benzoate                                                                           0.35   grams                                          20% Material                                                                  Pentylphenylmethoxy Benzoate                                                                          48     grams                                          Pentylphenylpentyloxy Benzoate                                                                        32     grams                                          Cyanophenylpentyl Benzoate                                                                            5.17   grams                                          Cyanophenylheptyl Benzoate                                                                            7.75   grams                                          Cyanophenylpentyloxy Benzoate                                                                         2.35   grams                                          Cyanophenylheptyloxy Benzoate                                                                         2.12   grams                                          Cyanophenyloctyloxy Benzoate                                                                          1.88   grams                                          Cyanophenylmethoxy Benzoate                                                                           0.705  grams                                          40% Material                                                                  Pentylphenylmethoxy Benzoate                                                                          36     grams                                          Pentylphenylpentyloxy Benzoate                                                                        24     grams                                          Cyanophenylpentyl Benzoate                                                                            10.35  grams                                          Cyanophenylheptyl Benzoate                                                                            15.32  grams                                          Cyanophenylpentyloxy Benzoate                                                                         4.7    grams                                          Cyanophenylheptyloxy Benzoate                                                                         4.23   grams                                          Cyanophenyloctyloxy Benzoate                                                                          3.76   grams                                          Cyanophenylmethoxy Benzoate                                                                           1.41   grams                                          40% MOD                                                                       Pentylphenylmethoxy Benzoate                                                                          36     grams                                          Pentylphenylpentyloxy Benzoate                                                                        24     grams                                          Cyanophenylpentyl Benzoate                                                                            16     grams                                          Cyanophenylheptyl Benzoate                                                                            24     grams                                          ______________________________________                                    

The encapsulating medium forming respective capsules 32 should be of atype that is substantially completely unaffected by and does not affectthe liquid crystal material. Various resins and/or polymers may be usedas the encapsulating medium. A preferred encapsulating medium ispolyvinyl alcohol (PVA), which has a good, relatively high, dielectricconstant and an index of refraction that is relatively closely matchedto that of the preferred liquid crystal material. An example ofpreferred PVA is an about 84% hydrolized, molecular weight of at leastabout 1,000, resin. Use of a PVA of Monsanto Company identified asGelvatol 20/30 represents the best mode of the invention.

A method for making emulsified or encapsulated liquid crystals 11 mayinclude mixing together the containment or encapsulating medium, theliquid crystal material, and perhaps a carrier medium, such as water.Mixing may occur in a variety of mixer devices, such as a blender, acolloid mill, which is most preferred, or the like. What occurs duringsuch mixing is the formation of an emulsion of the ingredients, whichsubsequently can be dried eliminating the carrier medium, such as water,and satisfactorily curing the encapsulating medium, such as the PVA.Although the capsule 32 of each thusly made encapsulated liquid crystal11 may not be a perfect sphere, each capsule will be substantiallyspherical in configuration because a sphere is the lowest free energystate of the individual droplets, globules or capsules of the emulsion,both when originally formed and after drying and/or curing.

The capsule size (diameter) preferably should be uniform in the emulsionfor uniformity of operation with respect to effect on incident light andresponse to electric field. Exemplary capsule size range may be fromabout 0.3 to about 100 microns, preferably 0.3 to 30 microns, especially3 to 15 microns, for example 5 to 15 microns.

Various techniques may be employed to form the support medium 12, whichmay be of the same or similar material as the encapsulating orcontainment medium. For example, the lower support medium 12b may beformed using a molding or casting process. The electrode 13 and liquidcrystal material may be applied for support by that medium 12b. Theelectrode 14 may be applied, e.g. by printing. Thereafter, the uppersupport medium portion 12a may be poured or cast in place to completeenclosing the encapsulated liquid crystal material and the electrodes.Alternatively, the support medium portions 12a, 12b may be asubstantially transparent plastic-like film or a plate of glass, as isdescribed in Example 1, for example.

The reflectance medium 18, if a solid, for example, may be applied tothe support medium portion 12b by a further casting or moldingtechnique, and a lower coating 21 of black or colored light absorbingmaterial may be applied to the back surface of the reflectance medium18, i.e. the surface remote from the interface thereof with the lowersupport medium portion 12b. Alternatively, the reflectance medium may bean air or other fluid gap between the support medium portion 12b and theabsorber 21, or a tuned dielectric layer may be applied by conventionalevaporation technique directly to the bottom surface of the lowersupport medium portion 12b in place of the reflectance medium 18, aswill be described further below.

The following are several examples of materials and methods for makingliquid crystal display devices and operational characteristics thereofin accordance with the present invention.

EXAMPLE 1

An example of the isotropically scattering material was produced bymixing about 2 grams of 8250 (an ester by American Liquid Xtal) nematicliquid crystal with about 4 grams of a 20% solution of Airco 405polyvinyl alcohol (the other 80% of such solution was water). Thematerial was mixed in a small homogenizer at low shear to form anemulsion. Using a doctor blade at about a 5 mil setting the emulsion wascoated on an electrode of Intrex material already in position on apolyester film base of about 5 mils thickness. Such film was that knownas Mylar. Another sheet of such film with such an electrode was placedon the encapsulated liquid crystal layer, thus sandwiching the latterbetween the respective electrodes and films. The individual encapsulatedoperationally nematic liquid crystal capsules or particles were about 4to 5 microns in diameter and the total layer of encapsulated liquidcrystal material was about 20 to 30 microns thick.

The device made according to Example 1 was tested. The resultingmaterial scattered light in a zero electric field (hereinafter usuallyreferred to as a zero field or field off condition) condition. In anapplied field of 10 volts the scattering decreased and at 40 voltsscattering stopped altogether.

Although a homogenizer was used, other types of mixers, blenders, etc.,may be used to perform the desired mixing.

EXAMPLE 2

An example of the isotropically scattering material was produced bymixing about 2 grams of 8250 nematic liquid crystal with about 4 gramsof a 22% solution (78% water) of Gelvatol 20/30 (by Monsanto) polyvinylalcohol. The material was mixed in a small homogenizer at low shear toform an emulsion. The emulsion was coated on Intrex film electrode andMylar film polyester base, as in Example 1, with a doctor blade at a 5mil setting and the sandwich was completed as in Example 1. The nematiccapsules or particles were about 3 to 4 microns in diameter, and theencapsulated liquid crystal layer was about 25 microns thick.

The device made according to Example 2 was tested. The resultingmaterial scattered light in a zero or field-off electric fieldcondition. In an applied field of 10 volts the scattering decreased andat 40 volts scattering stopped altogether.

EXAMPLE 3

An example of the isotropically scattering material was produced bymixing about 2 grams of E-63 (a biphenyl by British DrugHouse, asubsidiary of E. Merck of West Germany) nematic liquid crystal withabout 4 grams of a 22% solution of Gelvatol 20/30 (by Monsanto)polyvinyl alcohol. The material was mixed in a small homogenizer at lowshear to form an emulsion. The emulsion was coated on Intrex filmelectrode and Mylar film polyester base with a doctor blade at a 5 milsetting and the sandwich was completed as above. The thickness of theencapsulated liquid crystal layer was about 25 microns; the nematiccapsules or particles were about 4 to 5 microns in diameter.

The device made according to Example 3 was tested. The resultingmaterial scattered light in a zero field or field-off condition. In anapplied field of 7 volts the scattering decreased and at 35 voltsscattering stopped altogether.

EXAMPLE 4

An example of the isotropically scattering material was produced bymixing about 2 grams of 8250 liquid crystal with about 4 grams of a 22%solution of Gelvatol 20/30 polyvinyl alcohol. The material was mixed ina small homogenizer at low shear to form an emulsion. The emulsion wascoated on Intrex film electrode and Mylar polyester film base with adoctor blade at a 5 mil setting and the sandwich was completed as above.The thickness of the encapsulated liquid crystal layer was about 25microns; the nematic capsules or particles were about 4 to 5 microns indiameter.

To improve the emulsion stability and coating uniformity 0.001% of GAFLO 630 non-ionic surfactant (detergent) was added before the mixingstep. Improved performance instability of the emulsion and in coating ofthe emulsion onto the electrode/polyester film base were noted. Theoperational results were otherwise substantially similar to thosedescribed above with respect to Example 1.

Thus, it will be appreciated that in accordance with the invention asurfactant, preferably a non-ionic surfactant, a detergent, or the likemay be mixed with the encapsulated liquid crystal material prior todepositing on the electrode coated film, as was just described above.

EXAMPLE 5

The steps of Example 1 were followed using the same materials as inExample 1 except that 1/8 inch glass plate was substituted for the Mylarfilm. Operation was substantially the same as was described with respectto Example 1.

EXAMPLE 6

A mixture was formed of 8250 nematic liquid crystal and a solution of15% AN169 Gantrez in 85% water. Such Gantrez is poly(methyl vinylether/maleic anhydride), a polymaleic acid product, of GAF Corporation.The mixture was of 15% liquid crystal and 85% Gantrez as the containmentmedium. The mixture was homogenized at low shear to form an emulsion,which was applied to an electrode/support film as above; such supportfilm was about 1.2 mils thick. After drying of the emulsion, theresulting liquid crystal emulsion responded to an electric fieldgenerally as above, scattering when in field-off condition, showing athreshold of about 7 volts to begin reducing scattering, and having asaturation level of substantially no scattering at about 45 volts.

Another example of an acid type containment medium useful in theinvention is carbopole (carboxy polymethylene polymer by B. F. GoodrichChemical Company), or polyacid.

In accordance with the invention, other types of support media 12 thatmay be used include polyester materials; and polycarbonate material,such as Kodel film. Tedlar film, which is very inert, also may be usedif adequate adhesion of the electrode can be accomplished. Such media 12preferably should be substantially optically transparent.

In accordance with the invention, several different polymer containmentmedia that may be used are listed in Chart I below. The chart alsoindicates several characteristics of the respective polymers.

    ______________________________________                                        CHART I                                                                                                     Molec-                                                                              Temperature                               Containment         %         ular  &                                         Medium    Viscosity Hydrolyzed                                                                              Weight                                                                              % Solutions                               ______________________________________                                        20/30     4-6 CPS   88.7-85.5 10,000                                                                              4% at 20° C.                       Gelvatol, by                                                                  Monsanto                                                                      Company                                                                       40/20     2.4-3 CPS   77-72.9  3,000                                                                              4% at 20° C.                       Gelvatol, by                                                                  Monsanto                                                                      Company                                                                       523, by   21-25     87-89     --    4% at 20° C.                       Air Products                                                                  And                                                                           Chemicals, Inc.                                                               72/60     55-60      99-100   --    4% at 20° C.                       Elvanol, by                                                                   DuPont Co.                                                                    405       2-4 CPS   80-82     --    4% at 20° C.                       Poval, by                                                                     Kurashiki                                                                     ______________________________________                                    

Other Gelvatol PVA materials that may be used include those designatedby Monsanto as 20-90; 9000; 20-60; 6000; 3000; and 40-10.

A preferred quantity ratio of liquid crystal material to containmentmedium is about one part by weight liquid crystal material to aboutthree parts by weight of containment medium. Acceptable encapsulatedliquid crystal emulsion operative according to the invention also may beachieved using a quantity ratio of about one part liquid crystalmaterial to about two parts containment medium, e.g., Gelvatol PVA.Moreover, although a 1:1 ratio also will work, generally it will notfunction quite as well as material in the ratio range of from about 1:2to about 1:3.

Turning now to FIGS. 4 and 5, a portion 60 of a liquid crystal displaydevice in accordance with the present invention is illustrated. Theportion or device 60 is a completion of the liquid crystal apparatus 10described above with reference to FIG. 1 in that plural encapsulatedliquid crystals 11, indeed plural layers thereof, are contained in asupport medium 12. The sizes, thicknesses, diameters, etc., of theseveral parts shown in FIGS. 4 and 5 are not necessarily to scale;rather the sizes are such as is necessary to illustrate the severalparts and their operation, as is described below, in accordance with theinvention.

The electrodes 13, 14 are employed to apply a desired electric field toeffect selective alignment of the liquid crystal material in the mannershown in FIG. 3, for example. Means other than electrodes may beemployed to apply some type of input to the display device 60 for thepurpose of effecting ordered or random alignment of the liquid crystal.

The encapsulated liquid crystals 11 are arranged in several layers 61within the display portion 60. The layers 61 may be divided into severalportions representing the various characters or portions of charactersintended to be displayed by the display 60. For example, the longerlefthand portion 61L of the layers 61 shown in FIG. 4 may represent asection view through one part of a well known 7-segment display pattern,and the relatively short righthand portion 61R of the layers 61 shown inFIG. 4 may represent a part of another 7-segment character display. Itwill be appreciated, though, that various patterns of liquid crystalmaterial may be employed in accordance with the present invention. Azone 62 of support medium 12 fills the area between the liquid crystallayer portions 61L, 61R. Subsequent reference to layers 61 will be inthe collective, i.e. referring to layer 61 as including the severallevels or layers comprising the same. As an example, the compositethickness of such layer 61 may be from about 0.3 mils to about 10 mils;uniform thickness is preferred for uniform response to electric field,scattering, etc.

It is significant to note that such an arrangement or pattern ofencapsulated liquid crystal material layer portions, such as at 61L and61R, separated at zone 62 by support medium 12 or other material isfacilitated, or even made possible due to the encapsulating or confiningof the liquid crystal in discrete containment media, such as is formedby the preferred stable emulsion. Therefore, especially on a relativelylarge size device such as a display, billboard, optical shutter, etc.,encapsulated liquid crystal material may be applied to the supportmedium 12 only where it is required to provide the selectable opticalcharacteristics. Such patterning of the encapsulated liquid crystalmaterial can in some instances, then, appreciably reduce the amount ofsuch material required for a particular application. Such patterning isfurther made possible consistent with desired operation of a deviceusing encapsulated liquid crystal material in accordance with theinvention due to the functional operation thereof as will be describedin detail below.

The display 60 may be used, for example, in an air environment, such airbeing represented by the reference numeral 63, and the air forms aninterface 64 at the viewing side or from the viewing direction 20 withthe support medium 12. The index of refraction N of the external medium63 is different from the index of refraction N' of the encapsulatingmedium 12, the latter usually being larger than the former. As a result,a beam of light 65, which arrives generally from the viewing direction20, passing through the interface 64 into the support medium 12 will bebent toward the normal, which is an imaginary line 66 perpendicular tothat interface 64. That light beam 65a inside the support medium 12 willbe closer to normal than the incident beam 65 satisfying the equationrelationship N Sine θ=N' Sine θ', wherein θ is the angle of the incidentlight beam 65 with respect to the normal and θ' is the angle of thelight beam 65a with respect to normal. Such mathematical relationshipwill apply at the interface 19, as follows: N' Sine θ'=N" Sine θ". Toachieve the desired total internal reflection in accordance with theinvention, the index of refraction N" of the reflectance medium 18 issmaller than the index of refraction N' of the support medium 12.Accordingly, if the light beam 65a, for example, were able to and didpass through the interface 19, it would be bent away from the normal atthe interface 19 to the angle θ" with respect to normal. Actually, sincethe light beam 65, 65a is not scattered off course by the liquid crystalmaterial in layers 61, i.e., because it passes through the zone 62, itwill indeed likely exit through the interface 19.

Continuing to refer particularly to FIG. 4, operation of a liquidcrystal display 60 in accordance with the invention is now described.The operationally nematic liquid crystal 30 is in distorted or randomalignment due to existence of a field-off condition. Incident light beam70 enters the support medium 12 at the interface 64 and is bent as thelight beam 70a that impinges as incident light on the layer 61 ofencapsulated liquid crystal. The random or distorted encapsulated liquidcrystal material will isotropically scatter the light incident thereon.Therefore, there are several possibilities of how such incident lightbeam 70a would tend to be scattered, as follows:

A. For example, one possibility is that the incident light beam 70a willbe directed according to the dotted line 70b toward the interface 19.The angle at which the light beam 70b impinges on the interface 19 iswithin the illustrated solid angle α (defined in the planar direction ofthe drawing of FIG. 4 by the dashed lines 71) of a so-called cone ofillumination. Light falling within such solid angle α or cone ofillumination is at too small an angle with respect to normal at theinterface 19 to be totally internally reflected at that interface;therefore, the light beam 70b will pass through interface 19 whilebending away from the normal to form the light beam 70c. Light beam 70cpasses into the reflectance medium 18 and is absorbed by layer 21.

B. Another possibility is that the light beam 70a will be isotropicallyscattered in the direction of the light beam 70d outside the cone angleα. Total internal reflection will occur at the interface 19 causing thelight beam 70d to be reflected as light beam 70e back to the layer 61 ofencapsulated liquid crystal material where it will be treated as anotherindependently incident light beam thereto, just like the light beam 70afrom which it was derived. Therefore, such light beam 70e will undergoisotropic scattering again as is described herein.

C. Still another possibility is that the incident light beam 70a, orthat derived therefrom, such as the light beam 70e, will beisotropically scattered toward the interface 64 at an angle that is soclose to normal at that interface 64 that the light beam will passthrough the interface 64 into the "medium" 63, such as the air, to beviewed by an observer or observing instrument. The solid angle α' of acone of illumination, like the cone angle α mentioned above, withinwhich such scattered light beam 70e must fall to be emitted out throughthe interface 64 is represented by the single dot phantom lines 72.Light beam 70f represents such a light beam that is so emitted from thedisplay 60. It is that light, e.g. the sum of such emitted light beams70f, which exits at the interface 64 that causes the layer 61 ofencapsulated liquid crystals 11 to give the appearance of a white orbright character as viewed from the viewing direction 20.

D. Still a further possibility is that the light beam 70a may beisotropically scattered in the direction of the light beam 70g. Lightbeam 70g is outside the solid cone angle α' and, therefore, will undergototal internal reflection at the interface 64, whereupon the reflectedbeam 70h will impinge back on the layer 61 as an effectively independentincident light beam, like the beam 70e mentioned above and having asimilar effect.

The index of refraction of the electrodes 13,14 usually will be higherthan that (those) of the containment medium and support medium and thecontainment and support media indices of refraction preferably are atleast about the same. Therefore, the light passing from the containmentmedium into the electrode material will bend toward the normal, and thatpassing from the electrode into the support medium will bend away fromthe normal; the net effect of the electrode thus being nil orsubstantially negligible. Accordingly, the majority of total internalreflection will occur at the interfaces 19,64.

As viewed from the viewing direction 20, the zone 62 will appear dark orcolored according to the composition of the absorbent layer 21. This isdue to the fact that the light beam 65, 65a, 65b, representing themajority of light that passes through zone 62, will tend to pass throughinterface 64, support medium 12, the interface 19 and the reflectancemedium 18, being bent toward or away from the normal, at respectiveinterfaces as shown, ultimately being substantially absorbed by layer21.

Briefly referring to FIG. 5, the field-on or ordered alignment conditionand operation of the encapsulated liquid crystal layer 61 in the displaydevice 60 are shown. The encapsulated liquid crystals 11 in the layer 61of FIG. 5 are like those seen in FIG. 3. Therefore, like the light beam65, 65a, 65b which passes through the zone 62 and is absorbed by thelayer 21, the light beam 70, 70a, 70i will follow a similar path alsobeing transmitted through the aligned and, thus, effectively transparentor non-scattering layer 61. At the interface 19, the light beam 70a willbe bent away from the normal and subsequently light beam 70i will beabsorbed by the layer 21. Accordingly, whatever visual appearance thelight beam 65 would tend to cause with respect to an observer at theviewing location 20, so too will the light beam 70 cause the same effectwhen passing through the orderly aligned encapsulated liquid crystalmaterial. Thus, when the display 60, and particularly the encapsulatedliquid crystal material therein, is in the orderly aligned or field-oncondition, the area at which the liquid crystal is located will havesubstantially the same appearance as that of the zone 62.

It is noted that if either the incident beam 65 or 70 were to enter thesupport medium 12 at the interface 64 at such a large angle with respectto the normal there, and, therefore, ultimately to impinge on theinterface 19 at an angle greater than one falling within the so-calledcone of light angle α, such beam would be totally internally reflectedat the interface 19. However, such reflected light probably would remainwithin the support medium 12 due to subsequent transmission through thelayer of liquid crystal material 61 and subsequent total internalreflectance at the interface 64, etc.

In FIG. 6, the preferred reflectance medium 80 air is illustrated. InFIG. 6 primed reference numerals designate elements corresponding tothose designated by the same unprimed reference numerals in FIGS. 4 and5. The display 60' has an interface 19' formed with air 80. To achieveabsorbence of the light transmitted through the interface 19' and medium80, a black or colored absorber 81 may be positioned at a locationdisplaced from the interface 19'. The preferred absorber 81 is carbonblack which may be mounted on a support surface positioned generally asis shown in FIG. 6. The preferred liquid crystal is NM-8250 and thepreferred containment medium is PVA, as are mentioned above; and thepreferred support medium 12 is polyester. Moreover, it is preferred thatthe index of refraction of the support medium 12a, 12b, for example, andthat of the containment medium for the liquid crystal be at leastsubstantially the same; this helps to assure that the total internalreflection will occur primarily at the interfaces 19', 64' and not verymuch, if at all, at the interface between the containment medium andsupport medium; this minimizes optical distortion while maximizingcontrast. The display 60' functions substantially the same as thedisplay 60 described above with reference to FIGS. 4 and 5.

Referring, now, to FIGS. 7 and 8, a modified liquid crystal display 90is illustrated. The liquid crystal display 90 includes a support medium12 with a layer of encapsulated liquid crystal material 61, as above.However, at the interface 19 there is a tuned dielectric interferencelayer 91. The thickness of the dielectric layer 91, which is exaggeratedin the drawings, preferably is an odd whole number function or multipleof lambda divided by two such as 3λ/2, 5λ/2, etc., wherein λ is thewavelength of the light in the support display 60. The tuned dielectricinterference layer 91 may be applied to the back surface of the supportmedium 12 by conventional evaporation technique. Such dielectric layermay be comprised of barium oxide (BaO), lithium fluoride (LiF) or othermaterial that provides the desired optical interference function.Preferably such layer has a smaller index of refraction than the medium12 to obtain an interface 19 at which total internal reflection of lightwithin cone angle α will be internally reflected. A comprehensivedescription of optical interference is found in Optics by Born and Wolf,Fundamentals of Physics, 2nd Ed., 1981, Resnick and Halliday, pgs.731-735, and in University Physics by Sears and Zemansky, the relevantdisclosures of which are hereby incorporated by reference.

In the field-off/random liquid crystal alignment condition shown in FIG.7 the display 90 will function substantially the same as the display 60described above with respect to: (a) isotropic scattering of light bythe encapsulated liquid crystal material layer 61; (b) the totalinternal reflection of that light falling outside the solid angle coneα, this due to the interface 19 seen in FIG. 7, (or α' with respect tolight isotropically scattered to the interface 64), and; (c) thetransmitting of light, such as the light beam 70f, toward the viewingdirection 20 to give the appearance of a white character on a relativelydark background.

By use of the tuned dielectric interference layer 91 and opticalinterference, in the field-off condition the illumination effected ofthe encapsulated liquid crystal layer 61 is further enhanced.Specifically, the effective cone of light angle α becomes reduced to theangle φ shown in FIG. 7. Generally, an incident light beam 92 impingingon the interface 64 will be deflected as the light beam 92a which thenis incident on the layer 61. If the light beam 92a were isotropicallyscattered as beam 92b at an angle outside the original angle α, thetotal internal reflection operation described above with reference tothe display 60 will occur. However, if the light beam 92a isisotropically scattered as light beam 92c at an angle falling within thecone of light α but outside the cone of light φ, it will actually bereflected constructive optical interference will occur further toenhance the illumination of the encapsulated liquid crystal layer 61.

More particularly when the light beam 92c enters the tuned dielectricinterference layer 91, at least a portion 92d actually will be reflectedback toward the interface 19. At this interface 19, there will beconstructive interference with another incident light beam 93 increasingthe effective intensity of the internally reflected resultant light beam94, which is directed back toward the encapsulated liquid crystal layer61 enhancing the illumination thereof. The result of such constructiveinterference is that the display 90 yields more light beams scattered upto or reflected up to the layer 61 than in the display 60. However,there is a disadvantage in that the viewing angle at which the display90 will function effectively is less than the viewing angle at which thedisplay 60 will function effectively. Specifically, incident lightentering the support medium 12 at an angle equal or less than the angleδ with respect to the interface 64, will tend to be totally reflectedbecause the back or reflective surface of the tuned dielectricinterference layer 91 will tend to act as a mirror so that some contrastwill be lost in the display 90. The angle δ, if it exists at all, inconnection with the display 60 would tend to be smaller than the angle δof the display 90.

Light beams 95 and 96 (FIG. 7) that pass through the zone 62 of thedisplay 90 and light beams 92' (FIG. 8) that pass through the orderlyaligned (field-on) liquid crystal layer 61 and fall within the coneangle φ will undergo destructive optical interference. Therefore, fromthe viewing area 20 the zone 62 and the area where there is orderedfield-on liquid crystal will appear relatively dark, i.e. as a darkbackground relative to the white or brightly illuminated liquid crystallayer 61 portion that is field-off and scattering. If desired, anabsorber (black or colored) may be used beyond the layer 91. Also, thecolor of background may be altered as a function of the thickness of thelayer 91.

Turning now to FIG. 9, an example of a liquid crystal device 100 inaccordance with the invention is shown in the form of a liquid crystaldisplay device, which appears as a square cornered figure eight 101within the substrate or support medium 12, which in this case preferablyis a plastic material, such as Mylar, or may alternatively be anothermaterial, such as glass, for example. The shaded area appearing in FIG.9 to form the square cornered figure eight is comprised of one or morelayers 61 of encapsulated liquid crystals 11 arranged in one or morelayers on and adhered to the substrate 12. An enlarged fragmentarysection view of a portion of the figure eight 101 is illustrated in FIG.4 as the display 60, 60' or 90 described above with reference to FIGS.4-8.

Each of the seven segments of the figure eight 101 may be selectivelyenergized or not so as to create various numeral characters. Forexample, energization of the segments 101a and 101b would display thenumeral "1" and energization of the segments 101a, 101b, 101c woulddisplay the numeral "7". What is meant by energization here is theplacing of the respective segments in a condition to appear brightrelative to background. Therefore, energization means field-off orrandom alignment condition of, for example, segments 101a and 101b todisplay "1" while the other segments are in field-on, ordered alignment.

FIGS. 10 and 11 illustrate, respectively in fragmentary section andfragmentary isometric-type views, an embodiment of the inventionrepresenting the preferred arrangement of the liquid crystal layer 61"and electrodes 13", 14" in the support medium 12". In FIGS. 10 and 11,double primed reference numerals designate parts corresponding to thosedesignated by unprimed reference numerals in FIGS. 4 and 5, or primedreference numerals in FIG. 6. In particular, it is preferred accordingto the illustration of FIGS. 10 and 11 that the display device 60" havethe layer 61" and the electrode 13" substantially continuous over theentire or at least a relatively large portion of a display device. Theelectrode 13" may be connected, for example, to a source of electricalground potential. The electrode 14" may be divided into a plurality ofelectrically isolated electrode portions, such as those represented at14a, 14b, each of which may be selectively coupled to a source ofelectric potential to complete application of an electric field acrossthat liquid crystal material which is between such energized electrodeportion 14a or 14b and the other electrode 13". Therefore, for example,an electric field may be applied across the electrodes 14a, 13" causingthe encapsulated liquid crystal material falling substantially directlytherebetween to be in ordered, field-on alignment and, thus, effectivelyoptically transparent in the manner described above. At the same time,it may be that the electrode 14b is not connected to a source ofelectric potential so that the liquid crystal material between suchelectrode 14b and the electrode 13" will be in distorted or randomalignment and, therefore, will appear relatively bright from the viewingdirection 20". A small gap 120 between electrodes 14a, 14b provideselectric isolation therebetween to permit the just-described separateenergization or not thereof.

Briefly referring to FIG. 12, the preferred embodiment and best mode ofthe present invention is shown as the display 60'". In FIG. 12 thevarious portions designated by triple primed reference numeralscorrespond to those portions designated by similar reference numerals,as are described above. The display device 60" is made generally inaccordance with the numbered examples presented above. In particular,the lower support medium 12b'" is formed of Mylar film having an indiumdoped tin oxide Intrex electrode 13'" thereon; and the layer 61'" ofencapsulated liquid crystal material was applied to the electrode coatedsurface, as is shown. Several electrode portions 14a'", 14b'", etc. witha respective gap 120'" therebetween, were applied either directly to thesurface of the layer 61'" opposite the support medium 12b'" or to thesupport medium 12a'", and the latter was applied in the manner shown inFIG. 12 to complete a sandwich of the display device 60'". Moreover, thereflectance medium 80'" was air, and a carbon black absorber 21'"mounted on a support shown in FIG. 12 was placed opposite such air gap80'" from the support medium 12b'", as can be seen in the figure.Operation of the display device 60'" is according to the operationdescribed above, for example, with reference to FIGS. 4-6 and 10.

Referring to FIG. 13, an encapsulated liquid crystal 130 of the typedescribed in Example 7 below is schematically shown. Such capsule 130includes a spherical capsule wall 131 of containment material 132,operationally nematic liquid crystal material 133 inside the capsule,and a cholosteric chiral additive 134. The additive 134 is generally insolution with the nematic material 13, although the additive is shown inFIG. 13 at a central location because its function primarily is withrespect to the liquid crystal material remote from the capsule wall, asis described further below. The capsule 130 is shown in field-off,distorted condition with the liquid crystal material distorted in themanner described above, for example, with reference to FIG. 2. Theliquid crystal material most proximate the wall 131 tends to be forcedto a shape curved like the inner boundary of that wall, and there is adiscontinuity 135 analogous to the discontinuity 55 shown in FIG. 2.

EXAMPLE 7

The steps of Example 1 were followed using the same materials and stepsas in Example 1 except that 3% cholesterol oleate (chiral additive), acholosteric material, was added prior to the mixing step, and then suchmixing was carried out at very low shear. The resulting capsules weresomewhat larger than those produced in Example 1. The encapsulatedliquid crystal material was still operationally nematic.

In operation of the material formed in Example 7, it was found that thechiral additive improved (reduced) the response time of theoperationally nematic encapsulated liquid crystal material, particularlyin returning to the distorted alignment generally following the wallshape of the individual capsules, promptly after going from a field onto a field off condition. In such relatively large capsules, say abouton the order of at least 8 microns total diameter, when going to thefield off condition, it is the usual case that the liquid crystalmaterial adjacent the capsule wall would return to the distortedalignment following the capsule wall shape or curvature faster thanwould the liquid crystal material closer to the center of the capsule;this disparity tends to slow the overall response time of the material.However, the chiral additive induces a tendency for the structure totwist. This influence on the nematic material is most noticeable remotefrom the capsule wall and, thus, speeds up the return of such relativelyremote material to distorted alignment, preferably influenced by theshape of the capsule wall. Such chiral additive may be in the range ofabout 0.1% to about 8% of the liquid crystal material and a preferredrange of about 2% to about 5%. The amount may vary depending on theadditive and the liquid crystal and could even be outside the statedrange as long as the capsule remains operationally nematic.

It will be appreciated that the encapsulated liquid crystal 130 of FIG.13 may be substituted in various embodiments of the invention describedin this application in place of or in conjunction with the otherwiseherein described encapsulated liquid crystal material. Operation wouldbe generally along the lines described in Example 7.

Another additive also may be used to reduce and/or otherwise to controlthe viscosity of the liquid crystal during manufacturing of a device 60,for example. The reduced viscosity may have a positive effect onemulsion formation and/or on the process of applying the emulsion to anelectrode covered support medium 12. An example of such an additive maybe chloroform, which is water-soluble and leaves the emulsion on drying.

EXAMPLE 8

An emulsion was prepared using about 15 grams of 22% (the rest waswater) low viscosity, medium hydrolysis PVA; about 5 grams of 8250liquid crystal (of American Liquid Xtal) containing about 3%(percentages are with respect to the weight of the liquid crystal)cholesterol oleate, about 0.1% of a 1% (the rest was water) solution ofL.O. 630 surfactant, and 15% chloroform.

Such material was mixed at high shear for about 3 minutes. The capsulesproduced were about 1 to 2 microns in diameter. A layer of suchencapsulated liquid crystal was applied to an electrode covered supportmedium using a doctor blade at a gap 5 setting. The material was driedand operated generally as the materials described above.

A modified liquid crystal display device 140 in accordance with thepresent invention is shown schematically in FIGS. 14 and 15. In thedevice 140 the primary source of illumination is derived from a lightsource 141 at the so-called back or non-viewing side 142 of the displaydevice. More specifically, the display device 140 includes a layer 61 ofencapsulated liquid crystal between a pair of electrodes 13, 14supported on upper and lower support media 12a, 12b generally in themanner disclosed above, for example with reference to FIG. 12. Thereflectance medium 80 is an air gap, as was described in connection withthe preferred embodiment above.

A light control film (LCF) sold by 3-M Company is shown at 143; the onepreferrd is identified by product designationLCFS-ABRO-30°-OB-60°-CLEAR-GLOS-0.030. The light control film 143 is athin plastic sheet preferably of black substantially light absorbingmaterial that has black micro-louvers 144 leading therethrough from theback surface 145 toward the front surface 146 thereof. Such film or likematerial may be used in connection with the various embodiments of theinvention. Such film may in effect tend to collimate the light passingtherethrough for impingement on the liquid crystal material.

The micro-louvers function like a venetian blind to direct light fromthe source 141, for example light beams 150, 151, into and through thedisplay device 140, and particularly through the support medium 12 andliquid crystal layer 61, at an angle that would generally be out of theviewing angle line of sight of an observer looking at the display device140 from the viewing direction 20--this when the liquid crystal isaligned or substantially optically transparent. Such field-on alignedcondition is shown in FIG. 14 in which the light beams 150, 151 passsubstantially through the display device 140 out of the line of view.Moreover, light, such as light beam 152, incident on the display device140 from the viewing direction 20 will generally pass through thesupport medium 12 and aligned, field-on liquid crystal layer 61 forabsorption by the black film 143, which functions as the absorber 21'"in connection with FIG. 12, for example.

However, as is seen in FIG. 15, when the liquid crystal layer 61 is inthe field-off condition, i.e. the liquid crystal is distorted orrandomly aligned, the light beams 150, 151 from the source 141 areisotropically scattered by the layer of liquid crystal material 61causing total internal reflection and brightened appearance of theliquid crystal material in the manner described above. Thus, forexample, the beam 151 is shown being isotropically scattered as beam151a, totally internally reflected as beam 151b, and being furtherisotropically scattered as beam 151c which is directed out through theinterface 64 toward the viewing direction 20. The display device 140 ofFIGS. 14, 15 is particularly useful in situations where it is desirableto provide lighting from the back or non-viewing side. However, suchdisplay device also will function in the manner described above, forexample with respect to the display device 60'" of FIG. 12, even withoutthe back light source 141 as long as adequate light is provided from theviewing direction 20. Therefore, the device 140 may be used in daylight,for example, being illuminated at one or both sides by ambient lightwith or without the light source 141, and at night or in othercircumstances in which ambient lighting is inadequate for the desiredbrightness, for example, by using the illumination provided from thesource 141.

A display device 160 in FIG. 16 is similar to the display device 140except that the light control film 161 is cemented at 162 directly to,or is otherwise placed in abutment with the support medium material 12b.Total internal reflection would occur in the manner described above whenthe display device 160 is illuminated with light from the viewingdirection 20 due primarily to the interface 64 of the support medium 12awith air. There also may be some total internal reflection at theinterface 162. However, since the LCF film is directly applied to thesupport medium 12b, a relatively large quantity of the light reachingthe interface 162 will be absorbed by the black film. Therefore, in thedisplay device 160 it is particularly desirable to supply a backlighting source 141 to assure adequate illumination of the liquidcrystal material in the layer 61 for achieving the desired brightcharacter display function in accordance with the invention.

Briefly referring to FIG. 17, there is shown an alternate embodiment ofencapsulated liquid crystal material 200, which may be substituted forthe various other embodiments of the invention disclosed herein. Theencapsulated liquid crystal material 200 includes operationally nematicliquid crystal material 201 in a capsule 202 having preferably agenerally spherical wall 203. In FIG. 17 the material 200 is infield-off condition, and in that condition the structure 204 of theliquid crystal molecules is oriented to be normal or substantiallynormal to the wall 203 at the interface 205 therewith. Thus, at theinterface 205 the structure 204 is generally oriented in a radialdirection with respect to the geometry of the capsule 202. Moving closertoward the center of the capsule 202, the orientation of the structure204 of at least some of the liquid crystal molecules will tend to curvein order to utilize, i.e. to fill, the volume of the capsule 202 with asubstantially minimum free energy arrangement of the liquid crystal inthe capsule, for example, as is seen in the drawing.

Such alignment is believed to occur due to the addition of an additiveto the liquid crystal material 201 which reacts with the support mediumto form normally oriented steryl or alkyl groups at the inner capsulewall. More particularly, such additive may be a chrome steryl complex orWerner complex that reacts with PVA of the support medium (12) thatforms the capsule wall 203 to form a relatively rigid crust or wall witha steryl group or moeity tending to protrude radially into the liquidcrystal material itself. Such protrusion tends to effect the notedradial or normal alignment of the liquid crystal structure. Moreover,such alignment of the liquid crystal material still complies with theabove strongly curved distortion of the liquid crystal structure infield-off condition because the directional derivatives taken at rightangles to the general molecular direction are nonzero.

An example of such material 200 is presented below:

EXAMPLE 9

To a 5 gm sample of 8250 nematic liquid crystal was added 0.005 gm of a10% solution of Quilon M, a chrome steryl complex manufactured byDuPont, along with 3 gm of chloroform. The resulting material washomogenized at low shear with 15 gms of a 22% w/w solution of Gelvatol20/30 PVA (the remaining 78% of such Gelvatol solution was water).

The result was an encapsulated liquid crystal in which the capsule wallreacted with the Quilon M to form an insoluble shell.

By observation with polarized light it was determined that the capsulewall aligned the liquid crystal in a radial direction.

A film was cast on a Mylar support medium already having an Intrexelectrode thereon, as above, using a doctor blade with a gap setting of5 mils. The resulting film had a thickness of 1 mil on drying. Anauxiliary electrode was attached. The material began to align in thecapsule at 10 volts and was fully aligned at 40 volts. Such alignmentwould be like that shown in FIG. 3 above.

The invention may be used in a variety of ways to effect display ofdata, characters, information, pictures, etc. on both small and largescale. According to the preferred embodiment and best mode of theinvention, the liquid crystal material is placed in the support medium12 at only those areas where characters, etc., are to be formed. In thealternative, the layer 61 may extend across the entire support medium12, and only those areas where characters are to be displayed will haveelectrodes for controlling field-on/field-off with respect to theproximate portions of the liquid crystal layer 61. As an opticalshutter, the invention may be used to adjust the effective and/orapparent brightness of light viewed at the viewing side. Various otherdesigns also may be employed, as may be desired, utilizing the enhancedscattering effected by the total internal reflection and/or opticalinterference principles in accordance with the present invention.

STATEMENT OF INDUSTRIAL APPLICATION

The invention may be used, inter alia, to produce a controlled opticaldisplay.

I claim:
 1. Liquid crystal apparatus comprising liquid crystal means forselectively primarily scattering or transmitting light in response to aprescribed input, said liquid crystal means comprising operationallynematic liquid crystal material having positive dielectric anisotropy, asupport medium means for supporting said liquid crystal means, andreflecting means for effecting total internal reflection of lightscattered by said liquid crystal means, said support medium means havinga viewing side for emitting at least some light isotropically scatteredby said liquid crystal means and an opposite side relative to saidviewing side, and further comprising optical absorbing means forabsorbing light transmitted through said opposite side of said supportmedium means.
 2. The apparatus of claim 1, said liquid crystal meanscomprising at least one layer of encapsulated operationally nematicliquid crystal material in said support medium means, said liquidcrystal material having an ordinary index of refraction substantiallymatched to that of said support medium means to maximize opticaltransmission in the presence of an electric field and to effectsubstantial isotropic scattering in the absence of an electric field. 3.The apparatus of claim 2, said support medium means comprisingcontainment means for containing volumes of operationally nematic liquidcrystal material to distort the natural structure of the same when inthe absence of an electric field and to permit parallel alignment ofsuch structure in the presence of an electric field.
 4. The apparatus ofclaim 3, said containment medium means including wall means for efectingsuch distorted alignment causing said liquid crystal means to scatterlight incident thereon, and further comprising electrode means forapplying an electric field to said liquid crystal means to cause thelatter to change from a distorted alignment condition to generallyparallel alignment condition to transmit light incident thereon.
 5. Theapparatus of claim 4, further comprising circuit means for selectivelyenergizing said electrode means for applying such electric field.
 6. Theapparatus of claim 1, wherein said liquid crystal means is operative inthe absence of an electric field to scatter a substantial amount oflight at an angle exceeding the total internal reflection angle of saidsupport medium at such interface.
 7. The apparatus of claim 1, saidsupport medium means comprising containment medium means for containingsaid liquid crystal material in volumes, said volumes including wallmeans for distorting the natural structure of the liquid crystalmaterial in the absence of an electric field, the ordinary index ofrefraction of said liquid crystal material being substantially matchedto the index of refraction of said containment medium means to maximizetransmission of light in the presence of an electric field that causesgenerally parallel alignment of the liquid crystal structure and theextraordinary index of refraction of said liquid crystal material whenin such distorted structure alignment being different from that of saidcontainment medium means to effect scattering of light in the absence ofan electric field.
 8. The apparatus of claim 7, said support mediummeans further comprising a support for supporting said volumes of liquidcrystal material in said containment medium means.
 9. The apparatus ofclaim 1, said support medium means further comprising a substantiallyoptically transparent support means on both sides of said liquid crystalmaterial in said containment medium means for supporting and containingthe same.
 10. The apparatus of claim 9, said reflecting means comprisinga further medium having an index of refraction smaller than that of saidsupport means and forming an interface with respect to the latter tocause total internal reflection at said interface of at least some ofthe light scattered into said support means by said liquid crystalmeans.
 11. The apparatus of claim 1, respective media being at saidviewing and opposite sides, and the index of refraction of said supportmedium means being greater than the index of refraction of the medium atone of respectively such viewing and opposite sides, said reflectingmeans comprising an interface of such one of said sides with the mediumthereat to effect total internal reflection of light in said supportmedium means incident on such interface at an angle exceeding apredetermined cone of light angle at which light would be transmittedthrough such interface.
 12. The apparatus of claim 11, said interface atsuch one of said sides comprising an interface of said support mediummeans with air, and further comprising an optical absorbing meanspositioned in spaced relation to said interface for absorbing lighttransmitted through said interface, said optical absorbing meansdefining with such air and such interface an air gap.
 13. The apparatusof claim 11, wherein the index of refraction of said support mediummeans is greater than the indices of refraction of the media at both ofsaid viewing and opposite sides, and said reflecting means comprises theinterfaces of said sides with such media to effect such total internalreflection.
 14. The apparatus of claim 1, said absorbing meanscomprising a black absorber for absorbing at least substantially all ofthe light incident thereon.
 15. The apparatus of claim 1, said absorbingmeans comprising colored means for absorbing only one or more specifiedwavelengths of light.
 16. The apparatus of claim 1, the index ofrefraction of said support medium means being greater than the indicesof refraction of the media respectively at such viewing and oppositesides forming an interface therewith to effect total internal reflectionof light in said support medium means incident on such interface at anangle exceeding a predetermined cone of light angle at which light wouldbe transmitted through such interface, and said absorbing means beingpositioned in spaced apart relation from the interface of said supportmedium means and said medium at said opposite side.
 17. The apparatus ofclaim 1, said support medium means comprising a containment medium meansfor holding discrete quantities of said liquid crystal means incapsule-like volumes.
 18. The apparatus of claim 17, said support mediummeans further comprising a substantially optically transparent support.19. The apparatus of claim 18, said substantially optically transparentsupport comprising a polyester or polycarbonate material.
 20. Theapparatus of claim 19, further comprising electrode means for applyingan electric field to said liquid crystal means to cause the latter tochange from a random alignment structure condition distorted inconfiguration or shape by the walls of such respective capsule-likevolumes for scattering light incident thereon to generally parallelalignment condition to transmit light incident thereon.
 21. Theapparatus of claim 1, said reflecting means comprising means forreflecting light scattered by said liquid crystal means back to saidliquid crystal means to display relatively bright characters or the likeon a relatively dark background.
 22. The apparatus of claim 1, saidliquid crystal means comprising encapsulated liquid crystal.
 23. Thecombination of claim 1, said support medium means comprising acontainment medium, and said liquid crystal material and containmentmedium comprising an emulsion.
 24. A display device formed of the liquidcrystal apparatus of claim
 1. 25. The display device of 24, saidreflecting means comprising means for reflecting light scattered by saidliquid crystal means back to said liquid crystal means to displayrelatively bright characters or the like on a relatively darkbackground.
 26. Liquid crystal apparatus comprising liquid crystal meansfor selectively primarily scattering or transmitting light in responseto a prescribed input, said liquid crystal means comprisingoperationally nematic liquid crystal material having positive dielectricanisotropy, a support medium means for supporting said liquid crystalmeans, and reflecting means for effecting total internal reflection oflight scattered by said liquid crystal means, said support medium meanshaving a viewing side and an opposite side, respective media at saidviewing and opposite sides, and the index of refraction of said supportmedium means being greater than the index of refraction of the medium atone of respectively such viewing and opposite sides, said reflectingmeans comprising an interface of such one of said sides with the mediumthereat to effect total internal reflection of light in said supportmedium means incident on such interface at an total internal reflectionangle exceeding a predetermined cone of light angle at which light wouldbe transmitted through such interface, said liquid crystal means beingoperative in the absence of an electric field to scatter a substantialamount of light at an angle exceeding the total internal reflectionangle of said support medium means at such interface, said supportmedium means comprising containment medium means for containing saidliquid crystal material in volumes, said volumes including walls fordistorting the natural structure of the liquid crystal material in theabsence of an electric field, the ordinary index of refraction of saidliquid crystal material being substantially matched to the index ofrefraction of said containment medium means to maximize transmission oflight in the presence of an electric field that causes generallyparallel alignment of the liquid crystal structure and the extraordinaryindex of refraction of said liquid crystal material when in suchdistorted structure alignment being different from that of saidcontainment medium means to effect scattering of light in the absence ofan electric field, said interface at such one of said sides comprisingan interface of said support medium means with air, and furthercomprising an optical absorbing means positioned in spaced relation tosaid interface for absorbing light transmitted through said interface,said optical absorbing means defining with such air and such interfacean air gap.
 27. The apparatus of claim 26, wherein the index ofrefraction of said support medium means is greater than the indices ofrefraction of the media at both of said viewing and opposite sides, andsaid reflecting means comprises the interfaces of said sides with suchmedia to effect such total internal reflection.
 28. A method ofdisplaying a bright character or other information on a relatively darkbackground using liquid crystal material, comprising substantiallyisotropically scattering at least some light incident on such liquidcrystal material to form such character or other information, totallyinternally reflecting isotropically scattered light back to such liquidcrystal material to brighten the same, and absorbing at least some ofthe light transmitted by such liquid crystal material.
 29. The method ofclaim 28, further comprising effecting constructive optical interferencewith respect to at least some of such isotropically scattered light todirect the same incident on such liquid crystal material.
 30. The methodof claim 28, further comprising transmitting some of such isotropicallyscattered light to a viewing area.
 31. The method of claim 28, furthercomprising illuminating such liquid crystal material from opposite aviewing side thereof using incident light directed at an angleordinarily out of the viewing line of sight.
 32. The method of claim 28,further comprising selectively applying an electric field to such liquidcrystal material to align the same for transparency.